JP2000302549A - Piezoelectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric porcelain composition which is a Pb- piezoelectric porcelain composition containing lead iron-niobate and which is capable of being sintered at low temp. and is excellent in piezoelectric characteristics. SOLUTION: At least one element selected from the group of zinc, nickel, lithium and lead is added in the form of oxide or other compounds in a specified amount in order to sinter a Pb-piezoelectric porcelain composition containing lead iron-niobate at low temp and to improve piezoelectric characteristics. Further, at least one element of chromium and cobalt is added in the form of oxide or other compounds in the specified amount in order to sinter the Pb-piezoelectric porcelain composition containing lead ironniobate at low temp and to improve high temp. durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a piezoelectric ceramic composition.

[0002]

2. Description of the Related Art It is known that a piezoelectric ceramic composition comprising a composition of iron niobate, titanate and lead zirconate has a large electromechanical coupling coefficient, and its optimum sintering temperature is 1200.
A temperature of at least ℃ was required.

[0003]

When the piezoelectric ceramic composition based on iron niobate, titanic acid and lead zirconate is fired at a temperature of 1200 ° C. or more, the lead oxide as a main component evaporates violently. Needs to be fired in a high-quality sheath with a high degree of sealing while controlling the lead atmosphere. For this reason, the manufacturing process becomes complicated, and there is a problem that the life of the sheath used for firing is short and the manufacturing cost is increased.
Further, when a laminated piezoelectric ceramic material having an internal electrode formed in a sintered body is made of the above composition, the sintering temperature is high, so that it was necessary to use a high melting point noble metal as the internal electrode material.

The present invention provides a piezoelectric ceramic composition based on iron niobate, titanic acid, and lead zirconate, which is dense and has excellent piezoelectric properties, in which the sintering reaction is sufficiently performed even when firing at a relatively low temperature. It is intended to do so.

[0005]

According to the present invention, there is provided a piezoelectric ceramic composition containing lead iron niobate comprising at least one element selected from the group consisting of zinc, nickel, lithium and lead. By adding sintering, a dense sintered body having excellent piezoelectric properties can be obtained even when firing is performed at a temperature lower than the conventional firing temperature, and the intended purpose can be achieved.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention provides a lead-based piezoelectric ceramic composition containing lead iron niobate, which comprises zinc,
Nickel, lithium, a piezoelectric ceramic composition in which at least one element selected from the group of lead is added in the form of an oxide or other compound, zinc, nickel, lithium, which is highly effective as a sintering aid for the piezoelectric ceramic By adding lead, the sintering temperature of a lead-based piezoelectric ceramic composition containing lead iron niobate can be significantly reduced.

According to a second aspect of the present invention, there is provided the piezoelectric ceramic composition according to the first aspect, wherein the content of lead iron niobate is in the range of 0.01 to 0.10 mol. It defines an appropriate amount range of lead iron niobate from which a large electromechanical coupling coefficient can be obtained in a piezoelectric ceramic.

According to a third aspect of the present invention, zinc and nickel are converted to ZnO and NiO respectively by 0.1%.
２2% by weight of lithium converted to Li ₂ CO ₃ of 0.1
2. The piezoelectric ceramic composition according to claim 1, wherein at least one is added in a weight range of 1.5 to 1.5% by weight, which effectively acts on a lead-based piezoelectric ceramic composition containing lead iron niobate and has a sintering temperature. The optimum amounts of zinc, nickel, and lithium that reduce the amount of zinc are specified.

According to the invention of claim 4 of the present invention, lead is converted to P
0.5 to more than the amount specified in stoichiometry in terms of bO
3. The piezoelectric ceramic composition according to claim 1 or 2, further comprising 5% by weight of excess lead, which works effectively in a lead-based piezoelectric ceramic composition containing lead iron niobate to lower the sintering temperature. Is specified.

According to a fifth aspect of the present invention, there is provided the piezoelectric ceramic composition according to any one of the first to fourth aspects, wherein at least one of chromium and cobalt is added. Has the effect of improving the high-temperature deterioration performance of the characteristics that can withstand use in a relatively high temperature environment.

The invention according to claim 6 of the present invention is characterized in that at least one of chromium and cobalt is contained in a weight range of 0.002 to 0.5% by weight in terms of Cr ₂ O ₃ and Co ₃ O ₄ respectively. The piezoelectric ceramic composition according to claim 5, which has been added,
It defines the optimum amount of addition that can effectively act on a lead-based piezoelectric ceramic composition containing lead iron niobate and prevent deterioration of electrical characteristics at high temperatures.

An embodiment of the present invention will be described below.

As starting materials, high-purity PbO, TiO
₂ , ZrO ₂ , MgO, Nb ₂ O ₅ , NiO, ZnO, Fe
After weighing and mixing ₂ O ₃ , Cr ₂ O ₃ , Co ₃ O ₄ and Li ₂ CO ₃ so as to have the compositions shown in (Table 1) and (Table 2), the mixed powder was heated at 900 ° C. For 2 hours.

[0014]

[Table 1]

[0015]

[Table 2]

Next, the calcined material is wet-pulverized by a ball mill and then dried, and 7% of a 5% solution of polyvinyl alcohol is added as a binder to the piezoelectric ceramic material powder to perform granulation.

Next, the granulated powder is weighed at 1000 kg / cm.^TwoForm of
A disk having a diameter of 20 mm and a thickness of 1.6 mm was formed by forming pressure.
After that, firing is performed at each temperature in the range of 900 to 1300 ° C.
Was. The maximum sintering density was obtained for each composition
Each firing at which the firing temperature and its density and sintered density are maximized
The sample at the growth temperature is polished to a thickness of 1 mm, and electrodes are
After applying 3kV / mm in 30 ° C silicone oil
Polarization is performed by applying voltage, and the relative dielectric constant of the obtained piezoelectric ceramic material
Rate and electromechanical coupling coefficient are measured and the results are combined (see Table
This is shown in 1). In addition, each sample was evaluated for high-temperature durability.
After leaving in a thermostat at 110 ° C for 30 minutes, cool to room temperature
Measurement of the electromechanical coupling coefficient
(%) Was calculated and shown in (Table 2). In addition, (Table 1), (Table
PT in 2) is lead titanate (PbTiO)_Three), PZ
Lead ruconate (PbZrO_Three), PFN is iron, lead niobate
(Pb (Fe_1/3Nb_2/3) O_Three), PNN is nickel,
Lead niobate (Pb (Ni_1/3Nb_2/3) O_Three), PZN
Zinc, lead niobate (Pb (Zn_1/3Nb _2/3) O_Three), P
MN is magnesium, lead niobate (Pb (Mg_1/3N
b_2/3) O_Three) Are indicated by abbreviations.

As shown in (Table 1) and (Table 2), when the content of iron and lead niobate is in the range of 0.01 to 0.10 mol, the piezoelectric ceramic composition No. .1, 1
2, 14, 16, 18, and 20 all require firing at 1200 ° C. or higher in order to obtain a high sintered density and an electromechanical coupling coefficient. Porcelain composition Nos. 2 to 11, 13, 15, 17,
19, 21, 24, 25, 27, 28, 30, 31, 3,
3, 34, 36 to 39, 41 to 43 and 45 are 1075
Sintering at a relatively low temperature of ~ 1175 ° C is possible,
Moreover, both the relative permittivity and the electromechanical coupling coefficient are excellent.

However, the content of iron and lead niobate is 0.01 to
In the range of 0.10 mol, although the sintering temperature can be greatly lowered, Nos. 26 and 29 in which the additive of the present invention is added in a larger amount than the specified amount show that the sintered particles grow abnormally and the resistance of the porcelain increases. The bending strength is extremely reduced, and Nos. 32 and 35 have poor sinterability and the electromechanical coupling coefficient is sharply reduced. on the other hand,
No. 4 containing less than 0.01% by weight of iron and lead niobate
Nos. 6 and 47 have low sintering temperatures and excellent relative dielectric constants and electromechanical coupling coefficients, but have the disadvantage of poor heat resistance. In addition, iron and lead niobate contain more than 0.10% by weight of N.
No. 22 requires a sintering temperature of 1200 ° C. or more.
In the case of No. 23, the sintered density is low and is not practical.

Therefore, in order to obtain an excellent piezoelectric ceramic material which can be sintered at a low temperature and is practically useful, the lead-based piezoelectric ceramic composition containing iron and lead niobate requires a high content of iron and lead niobate. In the range of 0.01 to 0.10 mol, zinc: 0.1 to 2% by weight, nickel: 0.1 to 2% by weight,
Lithium: 0.1 to 1.5% by weight, Lead: 0.5 to 5% by weight, at least one additive is added to the basic piezoelectric ceramic composition, and the specified amount of chromium or cobalt is added. Although the addition of N improves heat resistance, both of them add 0.1%.
Nos. 40 and 44 with more than 5% by weight have a sharp decrease in the electromechanical coupling coefficient, so it is clear that the amount of addition must be limited to the range of 0.002 to 0.5% by weight.

[0021]

As described above, in the lead-based piezoelectric ceramic composition containing lead iron niobate according to the present invention, the content of iron and lead niobate is in the range of 0.01 to 0.10 mol, and zinc is added to the oxide. 0.1 to 2% by weight in terms of nickel, 0.1 to 2% by weight in terms of nickel, and 0.1 to 2% by weight in terms of lithium.
0.5 to 5% by weight, converted from lead to oxide
By adding at least one additive in the range, low-temperature sintering becomes possible, preventing a reduction in sheath life due to evaporation of lead oxide, and simplifying the manufacturing process,
It is also possible to achieve the base metalization of the electrode component of the laminate that is integrally sintered with the electrode, and to obtain a piezoelectric ceramic composition having an excellent relative dielectric constant and an excellent electromechanical coupling coefficient. Piezoelectric ceramics with excellent heat resistance by adding at least one of 0.02 to 0.5% by weight of chrome converted to oxide and 0.02 to 0.5% by weight of cobalt converted to oxide. It is possible to provide a composition.

Claims (6)

[Claims] 1. A piezoelectric ceramic comprising at least one element selected from the group consisting of zinc, nickel, lithium and lead added to a lead-based piezoelectric ceramic composition containing lead iron niobate in the form of an oxide or another compound. Composition. 2. The content of lead iron niobate in the range of 0.01 to 0.1.
The piezoelectric ceramic composition according to claim 1, wherein the composition is in a range of 10 mol. 3. Zinc and nickel are respectively ZnO, N
0.1 to ₂ % by weight of lithium in terms of iO is converted to Li ₂
The piezoelectric ceramic composition according to claim 1 prepared by adding at least one weight range of 0.1 to 1.5 wt% in terms of CO _3. 4. The piezoelectric ceramic composition according to claim 1, wherein lead is added in an amount of 0.5 to 5% by weight in excess of the amount specified in stoichiometry in terms of PbO. 5. The piezoelectric ceramic composition according to claim 1, wherein at least one of chromium and cobalt is added. 6. Chromium or cobalt is Cr ₂
O _3, Co ₃ O ₄ piezoelectric ceramic composition according to claim 5 by adding at least one weight range of 0.002 to 0.5 wt% in terms of.